docs: def download_files_if_not_in_manifest(files_iterator, output_path):
      """Download the given files to the given path, unless in manifest."""
      local_manifest = read_local_manifest(output_path)
      with open(get_local_manifest_path(output_path), 'a') as manifest_fh:
          for (file_name, width) in files_iterator:
              if is_file_in_manifest(file_name, width, local_manifest):
                  logging.info('Skipping file %s', file_name)
                  continue
              try:
                  download_file(file_name, output_path, width=width)
                  write_file_to_manifest(file_name, width, manifest_fh)
              except DownloadException, e:
                  logging.error("Could not download %s: %s", file_name, e.message)